This invention relates to a command device for a dobby which reciprocates the heald frame of a loom up and down.
A fabric having a desired structure and quality can be obtained by making a suitable selection as to the timing of up and down reciprocation of a heald frame. The timing of up and down reciprocation of the heald frame can be determined by controlling the drive mechanism of a dobby.
As a device for controlling the drive mechanism of a dobby, there is a command device which makes use of a pattern card perforated in a prescribed pattern.
In the above-mentioned command device, a feeler needle which is suspended from a horizontal needle extending out from the drive mechanism of the dobby is vertically displaced to scan the continuously driven pattern card, thereby mechanically detecting the presence or absence of the perforations. Results of the detection are then transmitted as an operational command to the drive mechanism of the dobby via the horizontal needle. Accordingly, the drive mechanism of the dobby is operated in such a manner that the heald frame is reciprocated up and down in accordance with the repeated reciprocation of the feeler needle into and out of the perforations in the pattern card.
A lower end portion of the feeler needle is however brought into contact with an edge portion of each perforation when the feeler needle is pulled upwardly from the perforation. This gives a damage to the edge portion of the perforation, leading to such problems that the control of the drive mechanism of the dobby becomes out of order and the durability and accuracy of the command device is lowered. These problems become more noticeable and serious as the dobby is operated at a higher speed, in other words, the moving speed of the pattern card increases.
It has conventionally been attempted to solve the above-described problems by reciprocating each feeler needle in horizontal directions at the same speed as the moving speed of the pattern card by means of a guide member which guides vertical movement of the feeler needle (see, Japanese patent publication No. 15136/76).
However, the above-described prior art device requires a special drive mechanism for reciprocating the guide member horizontally. In addition, an incorporation of such a special drive mechanism leads to another problem that the structure of the command device becomes complex.
Furthermore, the feeler needle is applied by a horizontal force while a guiding force is applied vertically to the feeler needle by the guide member. Thus, the guide member and feeler needle are both worn down to considerable extents due to friction therebetween, thereby making it difficult to maintain both of the feeler needle and guide member serviceable over a long time period.